Alcohol Proof Converter (ABV, US Proof, UK Proof)
Convert alcohol by volume to US proof and British proof, or either proof back to ABV, with how far over or under proof a spirit is on the old UK scale.
Results
What this tool does
Proof is an old way of stating alcohol strength. US proof is simply double the percentage by volume, so 40 % ABV is 80 proof. The older British scale, Sikes proof, put 100° proof at about 57.15 % ABV, so its degrees are roughly ABV × 7/4: 40 % ABV is about 70° proof, or '30 under proof'. The name comes from a story about spirit strong enough to still set gunpowder alight. Britain switched from proof to ABV in 1980, but you will still meet both scales on old bottles, in recipes and in US labelling, where ABV and proof are often printed side by side.
Formula
US proof = 2 × ABV · UK (Sikes) proof ≈ 7/4 × ABV · 100° UK proof ≈ 57.15 % ABV
Variables
| Symbol | Meaning | Unit |
|---|---|---|
md | Your figure is | — |
x | Your figure | — |
US | US proof | — |
UK | UK proof (Sikes) | — |
AB | Alcohol by volume | % |
OU | UK degrees over (+) or under (−) proof | — |
Worked example
- Your figure is1
- Your figure40
- US proof80.0
- UK proof (Sikes)70.0
- Alcohol by volume40.00 %
- UK degrees over (+) or under (−) proof-30.0
Limitations
- The default values are typical reference figures, not measurements of your situation. Replace them with your own data whenever you have it.
- The calculation runs at full precision and only the display is rounded. If you copy an intermediate value and retype it, small differences can appear.